Elliptical trainer with resilient unit

ABSTRACT

An elliptical trainer with a resilient unit includes a frame, an exercising unit axially disposed on the frame, a pedal unit pivotally mounted to the exercising unit, a damper for providing a damping resistance to the pedal unit, a guide unit for supporting the pedal unit and guiding the pedal unit to slide thereon, and a pair of resilient units respectively disposed in proximity to the pivoted junctions between the exercising unit and the pedal unit for enabling a pair of rear end portions of the pedal unit to be constantly kept far from a pair of pivot-connection portions of the exercising unit so that an inertial-elastic force is produced during operation of the elliptical trainer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fitness equipment technology and more particularly, to an elliptical trainer with a resilient unit.

2. Description of the Related Art

A fitness machine (US Patent Application 2013/0053218) consisting of a frame, a pedal unit, a driving unit and a damper is known. The frame comprises a base, an upright post fixedly connected to the base, a support rack connected between the upright post and the base, and a shaft fixedly connected between the upright post and the support rack. The pedal unit comprises a pair of rotary interlocking members respectively sleeved onto the shaft, a pair of sleeves respectively mounted around the rotary interlocking members, a pair of arm members respectively connected to the sleeves, and a pair of pedal shafts respectively pivotally connected to the arm members. The driving unit comprises a pair of detent cables slidably inserted through the support rack and connected between the rotary interlocking members and the pedal shafts. The damper is mounted at the frame and movable by the driving unit to impart a damping force to the pedal shafts.

This design of the fitness machine allows the user to exercise stepping exercises, and uses the elasticity of the detent cables to produce an inertial-elastic force during operation of the fitness machine. However, because these detent cables are respectively connected between the rotary interlocking members and the pedal shafts, the path of these detent cables is quite long, and the long opposite ends of the detent cables are exposed to the outside of the support rack. Thus, the exposed opposite ends of the detent cables can interfere with the user, and these detent cables are prone to elastic fatigue after a long period of use, and the maintenance of these detent cables is also very inconvenient.

SUMMARY OF THE INVENTION

The present invention has been achieved to overcome the above noted deficiencies. It is the main object of the present invention to provide an elliptical trainer with a resilient unit, which avoids interference with the user, has a simple structure, and facilitates maintenance.

To achieve this and other objects of the present invention, the elliptical trainer comprises a frame, an exercising unit, a pedal unit, a damper, a guide unit, and a pair of resilient units. The frame comprises a base. The exercising unit comprises a pair of arm members respectively pivotally connected to the frame and alternatively turnable and movable back and forth. Each arm member comprises a pivot-connection portion located at one end thereof and pivotally connected to the frame. The pedal unit comprises a pair of pedal shafts respectively pivotally connected to the arm members. Each pedal shaft comprises a rear end portion located at a rear end thereof. The damper is adapted for imparting a damping resistance to the pedal shafts. The guide unit is adapted for supporting the pedal shafts and guiding the pedal shafts to slide. The resilient units are respectively disposed in proximity to the pivoted junctions between the arm members and the pedal shafts, and adapted for constantly keeping the rear end portions of the pedal shafts far from the pivot-connection portions of the respective arm members.

The design of the elliptical training of the invention has the following effects: by means of the characteristic that the resilient units are respectively disposed in proximity to the pivoted junctions between the swinging portions of the arm members and the front end portions of the pedal shafts and the characteristic that the rear end portions of the pedal shafts are constantly kept far from the pivot-connection portions of the arm members, the elliptical trainer facilitates maintenance and can produce an inertial-elastic force and prevents the resilient units from interfering with the user during operation.

Other advantages and features of the present invention will be fully understood by reference to the following description in conjunction with the accompanying drawings, in which like reference signs denote like components of structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an oblique top elevational view of an elliptical trainer with resilient unit in accordance with a first embodiment of the present invention.

FIG. 2 is an exploded view of the elliptical trainer with resilient unit in accordance with the first embodiment of the present invention.

FIG. 3 is a front assembly view of the elliptical trainer with resilient unit in accordance with the first embodiment of the present invention.

FIG. 4 is a schematic operational view of the first embodiment of the present invention, illustrating the rear end portion of one pedal shaft kept far from the pivot-connection portion of the respective arm member.

FIG. 5 is another schematic operational view of the first embodiment of the present invention, illustrating the rear end portion of the pedal shaft moved toward the pivot-connection portion of the respective arm member.

FIG. 6 is a schematic front view of an elliptical trainer with resilient unit in accordance with a second embodiment of the present invention, illustrating a rear end portion of one pedal shaft kept far from a pivot-connection portion of a respective arm member.

FIG. 7 is a schematic operational view of the second embodiment of the present invention, illustrating the rear end portion of one pedal shaft kept and the pivot-connection portion of the respective arm member disposed in proximity to each other.

FIG. 8 is a schematic front view of an elliptical trainer with resilient unit in accordance with a third embodiment of the present invention, illustrating a rear end portion of one pedal shaft kept far from a pivot-connection portion of a respective arm member.

FIG. 9 is a schematic operational view of the third embodiment of the present invention, illustrating the rear end portion of one pedal shaft kept and the pivot-connection portion of the respective arm member disposed in proximity to each other.

FIG. 10 is a schematic front view of an elliptical trainer with resilient unit in accordance with a fourth embodiment of the present invention, illustrating a rear end portion of one pedal shaft kept far from a pivot-connection portion of a respective arm member.

FIG. 11 is a schematic operational view of the fourth embodiment of the present invention, illustrating the rear end portion of one pedal shaft kept and the pivot-connection portion of the respective arm member disposed in proximity to each other.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1, 2 and 3, an elliptical trainer with a resilient unit in accordance with a first embodiment of the present invention is shown. The elliptical exercise machine comprises a frame 10, an exercising unit 20, a pedal unit 30, a damper 40, a guide unit 50, a pair of resilient units 60, a handlebar unit 70, a constraint unit 80, and a shell 90.

The frame 10 comprises a base 11, and a support 12 fixedly mounted to a front side of the base 11. The support 12 comprises an upright post 13 located at a top side thereof, a transverse axle 131 fixedly and transversely extending across the upright post 13 near a top end thereof, and an extension bar 132 extended from the upright post 13 below transverse axle 131.

The exercising unit 20 comprises a pair of arm members 21 respectively pivotally connected to two opposite ends of the transverse axle 131 of the frame 10 and alternatively turnable back and forth about the transverse axle 131. Each arm member 21 comprises a pivot-connection portion 211 located at a top end thereof and pivotally connected to the respective one end of the transverse axle 131, a swinging portion 212 located at an opposing bottom end thereof, and a protruding rod 213 extended from the pivot-connection portion 211.

The pedal unit 30 comprises a pair of pedal shafts 31 respectively pivotally connected to the arm members 21 of the exercising unit 20, and a pair of pedals 32 respectively fixedly supported on the respective pedal shafts 31. Each pedal shaft 31 comprises a front end portion 311 pivotally connected to the swinging portion 212 of one respective arm member 21, and an opposing rear end portion 312. The pedals 32 are respectively fixedly mounted on the rear end portions 312 of the respective pedal shafts 31.

The damper 40 is adapted for imparting a damping resistance to the pedal shafts 31, comprising a rotatable wheel 41 pivotally mounted in the support 12, and a damping wheel 42 pivotally mounted in the support 12 and rotatable by the rotating wheel 41. The rotatable wheel 41 comprises an axle 411 axially located at the center and pivotally mounted in the support 12, and a pair of cranks 412 respectively fixedly connected to two opposite ends of the axle 411 in reversed directions.

The guide unit 50 comprises a pair of rockers 51 turnable relative to the frame 10, and a pair of connection rods 52 respectively pivotally coupled between the rockers 51 and the rotatable wheel 41 of the damper 40 for driving the rotatable wheel 41 to rotate. The rockers 51 have an inverted T-shape, each comprising a pivoting portion 511 pivotally connected to the support 12, a sliding guide portion 512 located at one side of the pivoting portion 511 for supporting one respective pedal shaft 31 and guiding the respective pedal shaft 31 to slide, and an interlocking portion 513 located at an opposite side of the pivoting portion 511 and pivotally connected to one respective connection rod 52. The connection rods 52 are respectively pivotally connected to the cranks 412.

The resilient units 60 are respectively disposed in proximity to the pivot-connection junctions between the swinging portions 212 of the arm members 21 and the front end portions 311 of the pedal shafts 31, each comprising a first link 61 pivotally connected to one respective arm member 21 between the swinging portion 212 and pivot-connection portion 211 of the respective arm member 21, a second link 62 pivotally connected between one respective pedal shaft 31 of the pedal unit 30 and the first link 61, and a resilient member 63. Each resilient member 63 comprises a first pivoting portion 631 pivotally connected to the swinging portion 212 of one respective arm member 21 or the front end portion 311 of one respective pedal shaft 31, and a second pivoting portion 632 pivotally connected to the pivoted point between the first link 61 and second link 62 of one respective resilient unit 60. The resilient force of the resilient members 63 enables the rear end portions 312 of the pedal shafts 31 of the pedal unit 30 to be constantly kept far away from the pivot-connection portions 211 of the respective arm members 21 of the exercising unit 20. In this embodiment, the resilient members 63 can be spring members, elastic cords or pneumatic cylinders.

The handlebar unit 70 comprises a pair of grips 71 respectively connected to the top ends of the arm members 21 above the transverse axle 131.

The constraint unit 80 comprises a pivot axle 81 pivotally mounted at the extension bar 132 of the frame 10, a pair of upper cranks 82 respectively fixedly connected to two opposite ends of the pivot axle 81 in reversed directions, and a pair of linkage rods 83 respectively pivotally connected between the upper cranks 82 and the protruding rods 213 of the arm members 21 of the exercising unit 20. The constraint unit 80 can limit the swinging stroke of the arm members 21 of the exercising unit 20.

The shell 90 is mounted on the frame 10 to shield the damper 40, a part of the guide unit 50 and the constraint unit 80.

When a user uses the elliptical trainer to exercise free-stepping and/or orbitrek exercises, as shown in FIGS. 3-5, the legs are used to apply pressure to the pedals 32 and pedal shafts 31 of the pedal unit 30 horizontally forwards and vertically downwards. As the pedals 32 and pedal shafts 31 of the pedal unit 30 are being alternatively moved, the front end portions 311 of the pedal shafts 31 will be forced against the swinging portions 212 of the respective arm members 21, causing the respective arm members 21 to turn back and forth about the transverse axle 131 of the frame 10. Subject to the functioning of the constraint unit 80, the pedal shafts 31, the arm members 21 and the grips 71 are moved back and forth in the predetermined paths. Further, when the pedal shafts 31 are being alternatively moved during the stepping operation and the rear end portion 312 of one pedal shaft 31 is moved far from the pivot-connection portion 211 of the respective arm member 21, as shown in FIG. 4, an inertial-elastic force is produced subject to the relative pivoting action between the first link 61 and second link 62 of the respective resilient unit 60 and the resilience of the respective resilient member 63. Further, as shown in FIG. 5, when the user releases the pressure from the pedal shaft 31, the rear end portion 312 of the respective pedal shaft 31 will be moved toward the pivot-connection portion 211 of the respective arm member 21. Therefore, when the pedal shafts 31 of the pedal unit 30 are being alternatively moved, the pedal shafts 31 are forced to impart a pressure to the sliding guide portions 512 of the respective rockers 51 of the guide unit 50, causing each rocker 51 to turn about the axis that extends through the pivoting portion 511 of the respective rocker 51 and the support 12, and thus, the rotatable wheel 41 is forced by the respective connection rod 52 of the guide unit 50 to rotate the damping wheel 42, causing generation of a damping resistance.

At this time, mating with the coordinated action of the user's legs, the resilient member 63 corresponding to the other pedal shaft 31 is forced to extend outwards, causing the rear end portion 312 of the pedal shaft 31 to be moved toward the pivot-connection portion 211 of the respective arm member 21, and thus, the pedal shafts 31 can be forced to turn the respective rockers 51 of the guide unit 50 about the axes that extend through the pivoting portions 511 of the respective rockers 51 and the support 12.

Thus, by means of the stepping action of the user's legs in an alternative manner and characterized in that the resilient units 60 are respectively disposed in proximity to the pivoted junctions between the swinging portions 212 of the arm members 21 and the front end portions 311 of the pedal shafts 31 and because the rear end portions 312 of the pedal shafts 31 are constantly kept far from the pivot-connection portions 211 of the arm members 21, an inertial-elastic force can be produced during operation of the pedal unit 30, and the resilient units 60 are prohibited from interfering with the user. Furthermore, this design facilitates maintenance.

In addition to the aforesaid operating modes, when the user intends to carry out a simple mode of stepping up and down, by using the two legs to alternatively impart a vertically downward pressure to the pedals 32 and pedal shafts 31 of the pedal unit 30, forcing the pedals 32 and the pedal shafts 31 to give a downward pressure to the sliding guide portions 512 of the respective rockers 51, and thus, subject to the functioning of the damper 40, a damping in the column vector is produced. At this time, the arm members 21 are almost prohibited from swinging.

When the user intends to carry out a sliding mode, by using the two legs to alternatively impart a horizontally forward pressure to the pedals 32 and pedal shafts 31 of the pedal unit 30, forcing the front end portions 311 of the pedal shafts 31 against the swinging portions 212 of the respective arm members 21 and causing the respective arm members 21 to turn about the transverse axle 131, and thus, subject to the functioning of the constraint unit 80, the swinging stroke of the arm members 21 are almost prohibited from swinging and the pedal shafts 31 is limited.

Therefore, the user can operate the elliptical trainer to selectively carry out the desired operating mode, such as free-stepping and orbitrek mode, sliding mode, or simple stepping mode.

Referring to FIGS. 6 and 7, an elliptical trainer with resilient unit in accordance with a second embodiment of the present invention is shown. This second embodiment is substantially similar to the aforesaid first embodiment with the exception that: each resilient unit 60′ comprises a link 61′ pivotally connected to one respective arm member 21 between the swinging portion 212 and the pivot-connection portion 211, a roller 62′ pivotally connected to the link 61′ and slidably supported on one respective pedal shaft 31, and a resilient member 63′. Each resilient member 63′ comprises a first pivoting portion 631′ pivotally connected to the swinging portion 212 of one respective arm member 21 or the front end portion 311 of one respective pedal shaft 31, and a second pivoting portion 632′ pivotally connected to the link 61′ adjacent to the roller 62′. The resilient force of the resilient members 63′ enables the rear end portions 312 of the pedal shafts 31 to be constantly kept far away from the pivot-connection portions 211 of the respective arm members 21. In this embodiment, the resilient members 63′ can be spring members, elastic cords or pneumatic cylinders. This second embodiment achieves the same effects as the aforesaid first embodiment does.

Referring to FIGS. 8 and 9, an elliptical trainer with resilient unit in accordance with a third embodiment of the present invention is shown. This third embodiment is substantially similar to the aforesaid second embodiment with the exception that: each resilient unit 60″ comprises a link 61″ pivotally connected to one respective pedal shaft 31 between the front end portion 311 and the rear end portion 312, a roller 62″ pivotally connected to the link 61′ and slidably supported on one respective arm member 21, and a resilient member 63″. Each resilient member 63″ comprises a first pivoting portion 631″ pivotally connected to the swinging portion 212 of one respective arm member 21 or the front end portion 311 of one respective pedal shaft 31, and a second pivoting portion 632″ pivotally connected to the link 61″ adjacent to the roller 62′. The resilient force of the resilient members 63″ enables the rear end portions 312 of the pedal shafts 31 to be constantly kept far away from the pivot-connection portions 211 of the respective arm members 21. In this embodiment, the resilient members 63″ can be spring members, elastic cords or pneumatic cylinders. This third embodiment achieves the same effects as the aforesaid first embodiment does.

Referring to FIGS. 10 and 11, an elliptical trainer with resilient unit in accordance with a fourth embodiment of the present invention is shown. This fourth embodiment is substantially similar to the aforesaid first through third embodiments with the exception that: each pedal shaft 31′ of the pedal unit 30′ further comprises an extension portion 313′ extended from said front end portion 311′ opposite to the rear end portion 312′, a top wall 314′ extended from the rear end portion 312′ to the extension portion 313′ and facing upwards, and an opposing bottom wall 315′ opposite to the top wall 314′ and facing downwards; each arm member 21 of the exercising unit 20 further comprises an inner wall 214 facing toward the rear end portion 312′ of the respective pedal shaft 31′ of the pedal unit 30′, and an outer wall 215 opposite to the inner wall 214; each resilient unit 6 comprises a resilient member 601 connected between one respective arm member 21 and one respective pedal shaft 31′; each resilient member 601 comprises a first positioning portion 602 connected to the outer wall 215 of one respective arm member 21 of the exercising unit 20, and a second positioning portion 603 connected to one respective pedal shaft 31′; the resilient members 601 of the resilient unit 6 provide a resilient force for enabling the rear end portions 312′ of the pedal shafts 31′ of the pedal unit 30′ to be constantly kept far away from the pivot-connection portions 211 of the respective arm members 21 of the exercising unit 20. In this embodiment, the second positioning portions 603 of the resilient members 601 can be selectively disposed in proximity to the top wall 314′ or the bottom wall 315′. Further, the resilient members 601 can be spring members, elastic cords or pneumatic cylinders. This fourth embodiment achieves the same effects as the aforesaid first embodiment does.

Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. 

What is claimed is:
 1. An elliptical exercise machine, comprising: a frame comprising a base; an exercising unit comprising a pair of arm members respectively pivotally connected to said frame and alternatively turnable back and forth, each said arm member comprising a pivot-connection portion located at one end thereof and pivotally connected to said frame; a pedal unit comprising a pair of pedal shafts respectively pivotally connected to said arm members, each said pedal shaft comprising a rear end portion located at a rear end thereof; a damper adapted for imparting a damping resistance to said pedal shafts; a guide unit adapted for supporting said pedal shafts and guiding said pedal shafts to slide; and a pair of resilient units respectively disposed in proximity to the pivoted junctions between said arm members and said pedal shafts and adapted for constantly keeping said rear end portions of said pedal shafts far from the respective said pivot-connection portions of said arm members.
 2. The elliptical exercise machine as claimed in claim 1, wherein said frame further comprises a support fixedly mounted to said base; said pivot-connection portions of said arm members of said exercising unit are respectively pivotally connected to said support of said frame; each said arm member further comprises a swinging portion located at an opposite end thereof remote from said pivot-connection portion; each said pedal shaft of said pedal unit further comprises a front end portion located at an opposing front end thereof remote from said rear end portion and pivotally connected to said swinging portion of the respective said arm member; said damper comprises a rotatable wheel, said rotatable wheel comprising an axle pivotally connected to said frame; said guide unit comprises a pair of rockers turnable relative to said frame, and a pair of connection rods respectively pivotally coupled between said rockers and said rotatable wheel of said damper for driving said rotatable wheel to rotate, each said rocker comprising a pivoting portion pivotally connected to frame, a sliding guide portion located at one side of said pivoting portion for supporting one respective said pedal shaft and guiding the respective said pedal shaft to slide, and an interlocking portion located at an opposite side of said pivoting portion and pivotally connected to one respective said connection rod; said resilient units are respectively disposed in proximity to the pivoted junctions between said swinging portions of said arm members and said front end portions of said pedal shafts.
 3. The elliptical exercise machine as claimed in claim 2, wherein each said resilient unit comprises a first link pivotally connected to one respective said arm member between said swinging portion and said pivot-connection portion of the respective said arm member, a second link pivotally connected between one respective said pedal shaft of said pedal unit and said first link and a resilient member, each said resilient member comprising a first pivoting portion pivotally connected to said swinging portion of one respective arm member or said front end portion of one respective pedal shaft and a second pivoting portion pivotally connected to said pivoted point between said first link and second link of one respective resilient unit, said resilient members providing a resilient force for enabling said rear end portions of said pedal shafts of said pedal unit to be constantly kept far away from said pivot-connection portions of the respective said arm members of said exercising unit.
 4. The elliptical exercise machine as claimed in claim 2, wherein each said resilient unit comprises a link pivotally connected to one respective said arm member between said swinging portion and said pivot-connection portion of the respective said arm member, a roller pivotally connected to said link and slidably supported on one respective said pedal shaft and a resilient member, each said resilient member comprising a first pivoting portion pivotally and selectively connected to said swinging portion of one respective said arm member or said front end portion of one respective said pedal shaft, and a second pivoting portion pivotally connected to said link adjacent to said roller, said resilient members providing a resilient force for enabling said rear end portions of said pedal shafts of said pedal unit to be constantly kept far away from said pivot-connection portions of the respective said arm members of said exercising unit.
 5. The elliptical exercise machine as claimed in claim 2, wherein each said resilient unit comprises a link pivotally connected to one respective said pedal shaft between said front end portion and said rear end portion of the respective said pedal shaft, a roller pivotally connected to said link and slidably supported on one respective said arm member and a resilient member, each said resilient member comprising a first pivoting portion pivotally and selectively connected to said swinging portion of one respective said arm member or said front end portion of one respective said pedal shaft and a second pivoting portion pivotally connected to said link adjacent to said roller, said resilient members providing a resilient force for enabling said rear end portions of said pedal shafts of said pedal unit to be constantly kept far away from said pivot-connection portions of the respective said arm members of said exercising unit.
 6. The elliptical exercise machine as claimed in claim 2, wherein each said arm member of said exercising unit further comprises an inner wall facing toward said rear end portion of one respective said pedal shaft of said pedal unit, and an outer wall opposite to said inner wall; each said resilient unit comprises a resilient member connected between one respective said arm member and one respective said pedal shaft, said resilient member comprising a first positioning portion connected to said outer wall of one respective said arm member of said exercising unit and a second positioning portion connected to one respective said pedal shaft; said resilient members of said two resilient units providing a resilient force for enabling said rear end portions of said pedal shafts of said pedal unit to be constantly kept far away from said pivot-connection portions of the respective said arm members of said exercising unit.
 7. The elliptical exercise machine as claimed in claim 6, wherein each said pedal shaft of said pedal unit further comprises an extension portion extended from said front end portion opposite to said rear end portion, a top wall extended from said rear end portion to said extension portion and facing upwards, and an opposing bottom wall opposite to said top wall and facing downwards; said second positioning portion of each said resilient member is disposed in proximity to one of said top wall and said bottom wall of one respective said pedal shaft.
 8. The elliptical exercise machine as claimed in claim 1, further comprising a handlebar unit and a constraint unit, said handlebar unit comprising a pair of grips respectively connected to respective top sides of said arm members, said constraint unit comprising a pivot shaft axially mounted on said frame, a pair of upper cranks respectively and fixedly connected to two opposite ends of said pivot shaft in reversed directions and a pair of linkage rods respectively pivotally coupled between said upper cranks and said grips.
 9. The elliptical exercise machine as claimed in claim 2, wherein said resilient members of said resilient units are selected from the group of spring members, elastic cords and pneumatic cylinders.
 10. The elliptical exercise machine as claimed in claim 2, further comprising a handlebar unit and a constraint unit, said handlebar unit comprising a pair of grips respectively connected to respective top sides of said arm members, said constraint unit comprising a pivot shaft axially mounted on said frame, a pair of upper cranks respectively and fixedly connected to two opposite ends of said pivot shaft in reversed directions and a pair of linkage rods respectively pivotally coupled between said upper cranks and said grips.
 11. The elliptical exercise machine as claimed in claim 3, further comprising a handlebar unit and a constraint unit, said handlebar unit comprising a pair of grips respectively connected to respective top sides of said arm members, said constraint unit comprising a pivot shaft axially mounted on said frame, a pair of upper cranks respectively and fixedly connected to two opposite ends of said pivot shaft in reversed directions and a pair of linkage rods respectively pivotally coupled between said upper cranks and said grips.
 12. The elliptical exercise machine as claimed in claim 4, further comprising a handlebar unit and a constraint unit, said handlebar unit comprising a pair of grips respectively connected to respective top sides of said arm members, said constraint unit comprising a pivot shaft axially mounted on said frame, a pair of upper cranks respectively and fixedly connected to two opposite ends of said pivot shaft in reversed directions and a pair of linkage rods respectively pivotally coupled between said upper cranks and said grips.
 13. The elliptical exercise machine as claimed in claim 5, further comprising a handlebar unit and a constraint unit, said handlebar unit comprising a pair of grips respectively connected to respective top sides of said arm members, said constraint unit comprising a pivot shaft axially mounted on said frame, a pair of upper cranks respectively and fixedly connected to two opposite ends of said pivot shaft in reversed directions and a pair of linkage rods respectively pivotally coupled between said upper cranks and said grips.
 14. The elliptical exercise machine as claimed in claim 6, further comprising a handlebar unit and a constraint unit, said handlebar unit comprising a pair of grips respectively connected to respective top sides of said arm members, said constraint unit comprising a pivot shaft axially mounted on said frame, a pair of upper cranks respectively and fixedly connected to two opposite ends of said pivot shaft in reversed directions and a pair of linkage rods respectively pivotally coupled between said upper cranks and said grips. 